You can download as many as you want.  But you can only license four states (printing or e-filing requires a license).

So if was never used, it is quite possible that you never 'licensed' that state.  In that case, just go ahead and download the state and use it.

In the event all four states were already licensed, you will need to contact Customer Service to change your license for that fourth state.

https://accountants-community.intuit.com/articles/1617365-proseries-hours-of-operation